THE MCSCULAB SYSTEM 195
In the Gorilla and Gibbon it is blended with the glutens minimus.
The pyriformis emerges from the pelvis through the great sciatic notch, and is inserted into the upper border of the great trochanter of the femur.
The obturator interims and gemelli are a closely-associated group of muscles. In the Chimpanzee the gemellus superior (fig. 36, K>, which is larger than the gemellus inferior, arises from the rudimentary ischial spine and its associated ligament. The gemellus inferior (fig. 36, E) arises from the deep surface of the ischiuii: and the outer surface of the tuber ischi:. The tendon of the obturator internus is separated from the ischium by a bursa. It receives the gemelli, and the combined mass is inserted into the femur above the trochanteric pit. In the Orang the gemellus inferior is larger than the gemellus superior: and the latter is represented, according to Hepburn (83) by a small slip from the obturator internus in the Gibbon. The obturator externus is similar in the Apes and Man.
The quadratus femoris arises from the ramus and outer surface of the tuber ischii, and it may be fused with the gemellus inferior. In the Gorilla it has a vertical attachment into the back of the great trochanter, but its insertion is rectangular in the other Apes. In the Orang it is considerably fused with the adductor inagnus.
The sartorius arises from a variable extent of the anterior border of the ilium. In the Chimpanzee it reaches down to the anterior inferior spine and up to near the anterior superior spine. The long ribbon-like belly is inserted into the upper third of the anterior border or inner surface of the shaft of the tibia. It is